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World Shelters Make it Complete with Papercrete

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JAS Interior Walls
Papecrete poster 1.jpg

Abstract[edit]

Fig 1: WorldShelters JAS Design (www.wired.com)

This webpage is about the "Papercrete Wall" Project from Engr 215 Spring 2010. The objective of this project is to design and build a rigid, cost effective inner wall of the World Shelter’s Just Add Sticks (JAS) system.

Papercrete Wall Project Plan[edit]

The designed inner wall system incorporates the use of papercrete, a weatherproof and fire resistant material. Papercrete makes use of the fibers found in paper and durability in concrete to form a rigid structure. The Papercrete Wall involves a wire mesh endoskeleton which provides the rigidity but still allows the wall piece to flex which provides protection from winds and the elements of nature. The imperative piece to the innovation and success associated with the designed wall is the papercrete exoskeleton; this is what sets it apart from other inner wall systems typically found in long-standing and relief structures. The papercrete component provides the insulation; wind and water proofing; fire resistancy; and the desired durability while maintaining a lightweight configuration.

Problem Statement and Criteria[edit]

Important Criteria

  • Zero Cost Goal: Spending for this project will be next to nothing due to prioritization of all World Shelters projects. Therefore, it is necessary to utilize free or negligible cost materials (transportation and construction inclusive).
  • Long Lasting: The project’s findings will double as a resource for other World Shelters projects. This increases the requested life span of the system from a couple years (relief) to as long as is feasible (lifetime).
  • Rigid and Durable: In order to achieve the desired longevity, the system must be durable. The wall system requires rigidity so it has the functionality of a normal inner wall structure. The wall will not have to bear load but must withstand normal living conditions.
  • Local Labor Use: Utilization of the Haitian work force drives self-sufficiency, reduces foreign dependency, and may possibly create more jobs.
  • Ease of Assembly: Construction of the wall must be a simplified procedure that many Haitian workers would be able to follow. The number of workers required is irrelevant to this criterion, but the expected mental and physical exertion per worker is critical.
  • Element Retardant: Must withstand degradation from surrounding elements as well as possible hazards like fires and hurricanes.
  • Insulative: More thermal insulation increases the value of the system.
  • Lightweight: More viable and reasonable wall structures maintain a lower mass which assimilates customary inner wall systems. This also ensures increased safety.
  • Aesthetics: In order to implement an inner wall structure that can integrate into the Haitian lifestyle and culture, how the wall looks and makes them feel is of some value.

Description of Final Project[edit]

Fig 2: AutoCAD or Papercrete Wall Section

The wall itself is 1.5 inches thick, allowing for the desired thin frame as well as tensile strength, and the surface area can be as large as needed for the structure. When taking into consideration the most durable and cost effective design, the recommended papercrete ratio is 1:3 (1 part paper to 3 parts cement). However, other ratios were tested and deemed satisfactory; if desired, other ratio options are possible.

Construction[edit]

Building a papercrete wall involves four primary steps: constructing the frame, mixing the papercrete, pouring the mold, and drying. If provided instructions and executed with efficiency, the building can be done in half an hour with the drying time dependent on the climate, weather conditions, and time constraints.

This frame is 3 ft x 3 ft and 3 inches deep(Figure 3).Necessary materials to construct the frame include: four pieces of wood one inch thick, about three inches wide and however long the dimensions of the wall will be; one slat of wood the dimensions of the desired wall plus one additional inch on every side; screws; drill/screwdriver; saw; and band clamp (optional). First cut the ends of the four pieces of wood at a 45° along the one inch side. These will be the sides of the frame. If a band clamp is available, strap the four sides so that the slanted ends fit together. Then screw the slat of wood that will be the baseboard to the top of the four strapped pieces. Remove the band clamp, flip the frame over, and begin making the papercrete. Before mixing the papercrete, the ratio of paper to concrete must be decided. The materials needed include the following: a scale; a mixing bucket; pounds of paper; concrete; water; drill with mixer drill bit; and wire mesh with the dimensions equal to that of the eventual wall.

First, weigh out the paper and cement to the previously decided ratio. Shred the paper; this is easy but laborious to do by hand. Drop the appropriate weight of shredded paper and concrete into the bucket and add just enough water to make a slurry (Figure 3a-b). The amount of water does not need to be precise, just thick enough to be moved around by hand. Additionally, if there are no time constraints on the drying process, all the water will dry eventually. If there are time constraints, compression can be used, effectuating the amount of water as inconsequential. Mix the contents in the bucket using the drill and the mixer drill bit. Mix until the paper is ground up and the slurry looks homogenous.

The last step of the laying process: setting the second coating of papercrete (Figure 3c).Now lay the mold into the frame previously built. By hand, place the slurry into the mold so that the base is covered with papercrete. Then place the wire mesh on top; make sure the wire is flat before it is put into the mold so the mold dries flat. Lastly, lay more papercrete on top so no wire is visible. Now, it needs to dry. If drying by air and with time, cover the wall with a waterproof material but leave space between the edges of the frame and the cover to allow ventilation. If desired, uncover when the weather permits (the mold will not hold up well under rain while drying).

Compressing the mixture with a sheer force allows for a shorter drying time and a more compacted product( Figure 3d), effectively increasing rigidity. Compression can be done simply by placing a slat of wood just big enough so it sits on top of your mold inside the frame. Put the whole system between a car and a car jack and crank the car up. This will drain out almost all the water; the remaining water will evaporate upon standing.

Costs[edit]

Item Amount Cost Total
1/2in Steel Wire mesh 6 $1.19 $7.14
8'x4' Piece of Plywood 1 $14.98 $14.98
Concrete 60lb Ready Mix 1 $3.99 $3.99
Pine Board 1"x4"x12' 1 $5.60 $5.60
Drill Paint Mixer 1 $2.99 $2.99
1/4lb Screws 1 $1.00 $1.00
Total $35.70

Test Result[edit]

Fig 5: Flex Test 50lb
Our prototype with the recommended ratio of cement to paper was used to perform a flame and resistance test. Once the prototype was made and dried, a flame test was done by holding it next to a 10,000 BTU flame for a period of 2 minutes.
Fig 4: Flame test
The prototype appeared to be fireproof and insulative; as the surface of it charred, it didn’t corrode or disintegrate and the side exposed to the flame was cool enough to touch and the other side remained unaffected. The resistance test was performed by throwing the prototype from an elevation of about five feet to the floor inducing as much velocity as possible with the human arm. The prototype stood up fairly well to this test as it proved its flexibility by bending. However, the force applied by the arm was not directly perpendicular to the floor so it experienced a bending force. Because of this angle, it split along the wire skeleton upon hitting the floor. This cracking may have been due to the fact that the prototype was not completely dry and therefore the bonds between the two slabs of papercrete may not have solidified. Additionally, when the wall is implemented into the structure it will be attached with zip ties lacing through the papercrete and wire core, bolstering the binding within the wall. We also conducted a flex test, where we suspended our same between two paint cans and added weight on the center. The sample bent but did not break due to the wire core within.

Discussion and Next Steps[edit]

After all of our research and testing we have concluded that the best ration of paper to concrete is 1 part paper to 5 parts concrete. We have also concluded that the mix would be better if the rocks from the mix where sifted out, allowing for am smoother mix and a lighter product when done.

  • Testing may continue to find the best wire spacing for the mesh core
  • Testing also may continue to find the best ratio.

References[edit]